Statistical analysis
Qualitative data is presented with absolute and relative frequencies
(%). Depending on the distribution (normal or not), quantitative data
is presented with average value, standard deviation, median and
intra-quatrile range. Regularity was checked using the
Kolmogorov-Smirnov criterion, and graphically with the use of
histograms. The correlation between data and serum vitamin D or AMPs
nasal fluid levels was determined with the use of Mann-Whitney and
Kruskal-Wallis criteria for qualitative factors with two or more
categories respectively, as well as with the correlation coefficient
Spearman’s rho for quantitative factors. Multiple linear and logarithmic
regression were used, in order to investigate how the severity of
bronchiolitis is affected by various potential confounders. Results are
presented in β regression coefficients, Odds Ratios (ΟR) and 95%
Confidence Intervals. Statistical analysis was performed with the
statistical package SPSS v25 and a probability value of p<0.05
was considered statistically significant.